1. Field of the Invention
The present invention generally relates to a transmission device, and more particularly to a transmission device of automatic document feeder.
2. The Related Art
Referring to FIG. 1, a traditional transmission device of automatic document feeder (not labeled) is adapted for being assembled in an automatic document feeder 100′. The automatic document feeder 100′ generally includes a passageway 10′ for transmitting papers. The passageway 10′ includes an input tray 14′, a paper-curved space 19′, a paper-feed channel 13′, a scanning channel 17′, a paper-out channel 15′ and a paper-out tray 16′ which are disposed in sequence from upstream to downstream, and a turn-over channel 18′ connected between the paper-feed channel 13′ and the paper-out channel 15′.
In order to make the paper transmitted through the above-mentioned passageway 10′, the automatic document feeder 100′ disposes a plurality of transmission devices along the passageway 10′. For example, the automatic document feeder 100′ includes a pickup device 20′ disposed at an entry end of the paper-feed channel 13′, a plurality of paper-feed roller 11′, and a correction roller 22′ disposed along the paper-feed channel 13′ and the paper-out channel 15′, and a paper-out device 40′ disposed at an exit end of the paper-out channel 15′. The paper-out device 40′ includes a paper-out roller 41′ and a pressure roller 42′ movably disposed under the paper-out roller 41′.
When the paper is scanned, the pickup device 20′ of the automatic document feeder 100′ will rotate clockwise to press downward on the papers which are placed in the input tray 14′ to start feeding the papers into the paper-feed channel 13′ of the automatic document feeder 100′, but at the time of the paper being fed into the paper-feed channel 13′, the correction roller 22′ and the paper-feed roller 11′ rotate anticlockwise or stop rotating, so the paper is curved in the paper-curved space 19′ to make the paper unable to be further fed into the paper-feed channel 13′, at the moment, a front edge of the paper is in alignment with the correction roller 22′. Then the correction roller 22′ and the paper-feed roller 11′ rotate clockwise, the paper is able to be further fed into the paper-feed channel 13′. At the moment, the pickup device 20′ stops rotating for avoiding feeding the paper again.
After the paper is transmitted to the paper-feed channel 13′, the paper-feed roller 11′ disposed between the paper-feed channel 13′ and the paper-out channel 15′ regularly rotates towards one direction, so as to transmit the paper to the scanning channel 17′. The automatic document feeder 100′ further includes a scanning unit (not shown), the scanning unit scans the paper. After completing scanning the paper, the pressure roller 42′ still presses against the paper-out roller 41′ to transmit the scanned paper to the paper-out tray 16′.
In general, when the automatic document feeder 100′ proceeds one-sided scanning, the pressure roller 42′ keeps pressing against the paper-out roller 41′ and further exerts a positive force on the paper. But when the automatic document feeder 100′ proceeds two-sided three-path scanning, at the time of the paper completing the one-sided scanning and being going to depart from the paper-out channel 15′, the paper-out device 40′ rotates anticlockwise and transmits the paper to the turn-over channel 18′ reversely. The paper passing through the turn-over channel 18′ is turned over and is further return to the paper-feed channel 13′. After turning over the paper, in order to avoid front and rear edges of the paper staggered at the position of the paper-out device 40′ to be clamped by the pressure roller 42′ to jam the paper, the pressure roller 42′ will descend to separate from the paper-out roller 41′.
From the above-mentioned description, it is able to be known that the pickup device 20′, no matter in action time point and the rotation direction, the paper-feed roller 11′ and the paper-out device 40′ have largish differences, the paper-feed roller 11′ rotates towards the same direction, the correction roller 22′, the paper-feed roller 11′, the pickup device 20′ and the paper-out device 40′ need to change rotation directions according to different positions of the paper, and the paper-out roller 41′ and the pressure roller 42′ of the paper-out device 40′ must be opened in a proper time. So the automatic document feeder 100′ mostly needs three motors or at least two motors, use clutches or use magnetic valves and so on to respectively drive the pickup device 20′, the correction roller 22′, the paper-feed roller 11′ and the paper-out device 40′.
However, the automatic document feeder 100′ mostly needs three motors or at least two motors that increases a volume of the automatic document feeder 100′ and a manufacturing cost of the automatic document feeder 100′.
In order to solve the problem described above, it is essential to improve the traditional transmission device of automatic document feeder, and the automatic document feeder 100′.